Template-Based Orbital Wall Fracture Treatment Using Statistical Shape Analysis

Computer-Aided Fracture Size Measurement in Orbital Fractures-An Alternative to Manual Evaluation

Objective

We aimed to present a novel semiautomated tool for orbital fracture size measurement and to compare the variability of the proposed method with traditional manual measurements.

Methods

Maximal anteroposterior (AP) and mediolateral (ML) dimensions of orbital fractures from computed tomography images were measured for 15 patients with unilateral orbital fractures by 2 surgeons manually and with a semiautomatic software. Variability was assessed with Bland-Altman limits of agreement plots and intra-class correlation coefficients (ICCs).

Results

The intra-observer ICCs in manual and automatic measurements were high, >0.9. The inter-observer ICCs in manual measurements were 0.926 (AP) and 0.631 (ML) and in automatic measurements 0.989 (AP) and 0.989 (ML). The ICCs for manual and semiautomated variability were 0.899 (AP) and 0.669 (ML). The differences were thus particularly pronounced in the ML dimensions. In addition, with the semiautomated technique, a total fracture area could be measured and compared with the total area of the bony orbit and a 3-dimensional reformatted image could be generated.

Conclusions

Intra- and inter-observer variability proved to be very low for measuring fracture maximal AP length and ML width, making both the manual and the semiautomatic methods feasible clinically. The semiautomatic fracture size analysis allows better observer-independent repeatability for fracture size measurements and provides the possibility for total fracture area measurements at any orbital bony site, even in challenging nonplanar topography.

Three-Dimensional Computer-Aided Analysis of 293 Isolated Blowout Fractures - Which Radiological Findings Guide Treatment Decision?

PURPOSE

Our study purpose was to clarify the extent of isolated unilateral orbital blowout fracture in relation to surgical treatment and other factors behind the treatment decision. The specific aim was to determine which computer-aided measurements based on radiological images associate with treatment choice.

METHODS

A retrospective cohort study was implemented on patients with an isolated unilateral orbital blowout fracture. Computer-aided measurement of fracture extent was performed. The study variables included treatment as primary outcome (surgical vs nonsurgical), post-traumatic orbital volume difference (mL) compared to contralateral orbit, fracture area (mm²), fracture depth (mm) as predictor variables, and age, sex, injury mechanism, side and site of orbital fracture and positions of recti muscles as explanatory variables. Postoperative outcomes were reported. Logistic regression analysis was used to determine the risk factors for surgery. The statistical significance level was set at P < .05.

RESULTS

Of 293 patients, 28.0% received surgical and 72.0% nonsurgical treatment. Volume difference, fracture area and fracture depth predicted surgical outcome (P < .001). In adjusted univariate regression analyses, fractures with moderate and severe displacement of recti muscles were more likely to receive surgical treatment than fractures with mild or no displacement (OR 6.15 and 30.75, respectively, P < .001). Isolated medial wall fractures were significantly less often (OR 0.05, P = .006) and patients with older age (OR 0.97, P = .013) slightly less often treated with surgery. Patients with preoperative symptoms had more often persisting postoperative symptoms than patients without preoperative symptoms.

CONCLUSIONS

Positions of the recti muscles are an independent radiological factor guiding orbital blowout fracture treatment decision. The bony fracture extent is a combination of volume difference, fracture area and fracture depth which are strongly correlated to each other. A computer-aided method significantly facilitates the systematic evaluation of bone fragments, and the extent of orbital fractures.

Surgical instrument to improve implant positioning in orbital reconstruction: a feasibility study

Adequate positioning of an orbital implant during orbital reconstruction surgery is essential for restoration of the pre-traumatised anatomy, but visual appraisal of its position is limited by the keyhole access and protruding soft tissues. A positioning instrument that attaches to the implant was designed to provide feedback outside the orbit. The goal of this study was to evaluate the accuracy of placement with the instrument and compare it with the accuracy of placement by visual appraisal. Ten orbits in five human cadaver heads were reconstructed twice: once using visual appraisal and once using the instrument workflow. No significant improvement was found for the roll (5.8° vs 3.4°, respectively, p=0.16), pitch (2.1° vs 1.5°, p=0.56), or translation (2.9 mm vs 3.3 mm, p=0.77), but the yaw was significantly reduced if the instrument workflow was used (15.3° vs 2.9°, p=0.02). The workflow is associated with low costs and low logistical demands, and may prevent outliers in implant positioning in a clinical setting when intraoperative navigation or patient-specific implants are not available.

Evaluation of the Midface by Statistical Shape Modeling

PURPOSE

The aim of this investigation was to generate a statistical shape model (SSM) of the midface and evaluate symmetry, gender aspects, and bone thickness.

METHODS

About 102 computed tomography scans were analyzed to create the SSM. This included segmentation, landmark attribution, and Procrustes and principal component analysis. Afterward, symmetry and gender differences were visualized by registration and color coding. Bone thickness was calculated by measuring the distance between outer and inner surfaces.

RESULTS

Symmetry was high in all models. The male model showed a more prominent forehead, nasal bones, and larger bizygomatic width. Bone thickness resembled the concept of vertical and horizontal maxillary pillars and buttresses.

CONCLUSIONS

SSM can be used to analyze midface morphology and help in virtual surgery planning. Calculation of bone thickness could also be a useful tool in surgical planning and biomechanics.

Analysis of Orbital Morphology and its Relationship With Eyelid Morphology

Correct anatomical reconstruction of the orbital wall for function and cosmesis is important; however, this is difficult because of the structure's complexity. The authors aimed to analyze and classify orbital morphology from computed tomography (CT) images and examine the relationship between orbital morphology and eyelid morphology in the Japanese population. CT images of 60 men (right side, 29; left side, 31) and 44 women (each side, 22) were included. The lengths of the orbital medial wall and floor in the coronal plane at the anterior, middle, and posterior planes of the orbit; angle between them; simotic index; and the thickness of upper eyelid were measured. Additionally, the presence or absence of double eyelids was evaluated. Non-paired Student's t test and Pearson correlation coefficient test were used for analysis. Orbital morphology was symmetrical on both sides, and men had a larger orbit than women. Orbital morphology was classified into 2 groups according to the posterior angle, and there was a difference between the groups in the simotic index. The difference between groups may represent a genetic difference between the Jomon and Yayoi people and not only provide a new classification for the orbit of the population but also be useful in orbital reconstruction.

Present and future for technologies to develop patient-specific medical devices: a systematic review approach

The main purpose of this investigation was to systematically review the literature regarding case studies on patient-specific implants and devices, with the goal of analyzing the process of developing custom-made medical devices. A content analysis was performed to identify design processes and methodologies implemented to develop devices such as implants adapted to bone geometries. Reverse engineering, computer-aided design, simulation of assets, and rapid prototyping technologies were selected according to their interoperability in a process framework for developing new products. Finally, results from the case studies and process stages identified in the consulted research were analyzed. These results showed a relationship between the scope and complexity of the process and the stage of technology integration of the patient-specific device development. The analyzed case studies were characterized by technical, scientific, and multidisciplinary components to achieve research goals. Likewise, integration of technologies using patient-specific technologies is needed for product development that converges into designing devices, such as implants, biomodels, and cutting drilling guides.

Investigating gender and ethnicity differences in proximal humeral morphology using a statistical shape model

Morphological variability in the shoulder influences the joint biomechanics and is an important consideration in arthroplasty and implant design. The objectives of this study were to quantify cortical and cancellous proximal humeral morphology and to assess whether shape variation was influenced by gender and ethnicity, with the overarching goal of informing implant design and treatment. A statistical shape model of the proximal humeral cortical and cancellous regions was developed for a training set of 84 subjects of both genders and different ethnicities. Cortical and cancellous bone geometries were reconstructed from CT scans, meshed with triangular elements, and registered to a template. Principal component analysis was applied to quantify modes of variation. Anatomical measurements were computed on the registered geometries to assess correlation with modes of variation. Parallel analysis identified six significant modes of variation, which accounted for 93% of variation in the training set and described scaling (Mode 1), inclination of the head (Modes 2 and 5), and shape of the greater tuberosity and neck region (Modes 3, 4, and 6). Size differences as described by Mode 1 were statistically significant for gender and ethnicity, where female and Asian subjects were smaller than male and Caucasian subjects, respectively; however, differences in other modes were not significant. Cortical thickness of the shaft after normalization by outer diameter was significantly larger for Asian subjects compared to Caucasian subjects. The statistical shape model quantified cortical and cancellous humeral morphology considering gender and ethnicity, providing descriptive data to support surgical planning, and implant design. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3043-3052, 2018.